Targeting of the retinal pigment epithelium (RPE) by means of a rapidly scanned continuous wave (CW) laser beam

• Published in: Lasers in surgery and medicine 2003-01, Vol.32 (4), p.252-264
• Main Authors: Brinkmann, Ralf, Koop, Norbert, Özdemir, Mustafa, Alt, Clemens, Schüle, Georg, Lin, Charles P., Birngruber, Reginald
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; fluorescence microscopy; Humans; In Vitro Techniques; Investigative techniques of ocular function and vision; Investigative techniques, diagnostic techniques (general aspects); Laser Coagulation - instrumentation; laser scanner; Medical sciences; melanosome; photocoagulation; Pigment Epithelium of Eye - injuries; Pigment Epithelium of Eye - surgery; Retinal Diseases - surgery; RPE damage; selective treatment; Swine; viability assay
• ISSN: 0196-8092; 1096-9101
• DOI: 10.1002/lsm.10150

Background and Objectives Selective treatment of the retinal pigment epithelium (RPE) by repetitively applying green μs‐laser pulses is a new method for retinal diseases associated with a degradation of the RPE, which spares the neural retina. We investigated an alternative approach to realize repetitive μs‐laser exposure by rapidly scanning a continuous wave (CW)‐laser beam across the RPE. Study Design/Materials and Methods An Ar+ laser beam (514 nm) with a diameter of 18.75 μm was repetitively scanned across porcine RPE samples in vitro providing an irradiation time of 1.6 μs per point on the central scan axis. RPE cell damage was investigated by means of the fluorescence viability assay Calcein‐AM. Results The ED50 cell damage is 305 mJ/cm2 when applying 10 scans with a repetition rate of 500 Hz. The threshold decreases with the number of scans, a saturation was found at 135 mJ/cm2 with more than 500 exposures applied. The depth of focus in beam direction is 350 μm, defined by an increase of the threshold radiant exposure by 20%. Conclusions Targeting of pigmented cells with high local resolution has been proved with a laser‐scanning device. Looking ahead selective RPE‐treatment, the adaptation of a laser‐scanning device on a slit‐lamp or into a modified retina angiograph seems to be an attractive alternative to the pulsed μs laser device. Lasers Surg. Med. 32:252–264, 2003. © 2003 Wiley‐Liss, Inc.